The principal objectives of this project are to study the regulation of hypothalamic B-endorphin by sex steroids; to study the release of hypothalamic B-endorphin into hypophyseal portal blood; to define the role of hypothalamic B-endorphin in the physiologic control of gonadotropin secretion in the presence and absence of sex steroids; and to study the secretion of B-endorphin into the peripheral plasma of patients with abnormal ACTH secretion. Methodology will include hypophyseal portal blood collection in the monkey as well as radioimmunoassay, gel filtration, and ion exchange chromatography to measure and characterize B-endorphin in the brain, pituitary, and portal plasma. The long term objective of this project is to determine whether changes in hypothalamic and hypophyseal portal blood B-endorphin are important in the physiologic regulation of gonadotropin secretion.